Process of separating plutonium values by electrodeposition



ately adjacent to the cathode.

United States Patent 3:. 2,830,939 PROCESS OF SEPARATING PLUTONIUM VALUES BY ELECTRODEPOSITION Arthur C. Wahl, St. Louis County, Mo., assignor to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Original application December 27, 1945, Serial No. 637,487. Divided and this application June 17, 1947, Serial No. 755,178

1 Claim. (Ci. 2.041.5)

This invention relates to a new process of separating plutonium values by electrodeposition from an aqueous solution.

An object of this invention is to provide electrolytic methods for the separation of plutonium from solution.

Another object of the present invention is to provide suitable methods for the electrodeposition of plutonium from solutions in hydroxy solvents.

Additional objects and advantages of the present invention will be apparent from the following description.

Plutonium is a strongly electropositive metal, not far below the alkali metals in the electromotive series, and it is therefore difficult to effect electrodeposition of metal; lic plutonium. We have found, however, that plutonium may readily be electrodeposited as an oxygenated compound by the electrolysis of suitable solutions of plutonium in hydroxy solvents.

Solutions from which plutonium may be electrodeposited in accordance with the present invention preferably contain plutonium in the form of plutonyl ion, PuO which may be reduced at the cathode to yield a hydrous oxide substantially insoluble under the conditions of electrolysis, or in the form of a cation which will hydrolyze to an insoluble compound in the layer of solution of low hydrogen ion concentration immedi- All of the common inorganic salts of plutonium are readily hydrolyzable and may suitably be employed in the present process. Plutonium chloride and plutonium nitrate are examples of suitable compounds. The plutonium in the electrolyte may initially be in any of its valence states or in an equilibrium mixture of dififerent valence states, and will be electrodeposited, either by anodic oxidation to PuOz++ with subsequent cathodic reduction, or by hydrolysis to a compound substantially insoluble in the solution of low hydrogen ion concentration in the immediate neighborhood of the cathode.

The solvent may suitably comprise any normally liquid hydroxy solvent, but is preferably an aqueous solvent.

Aqueous solutions for the electrodeposition of plutonium may suitably be acidified in order to provide adequate conductivity. If the desired plutonium concentration in the electrolyte exceeds the solubility concentration of plutonium hydroxide, or of a basic plutonium salt of one of the anions in the solution, the pH should be lowered in order to prevent precipitation of the plutonium. Inorganic acid solutions of about 0.1 N-1.0 N are generally satisfactory for this purpose. Considerably higher acid concentrations may cause the formation of negatively charged complex ions with resulting anodic deposition. For deposition only at the cathode, it is preferred to employ solutions having acid concentrations not substantially greater than 1 N.

Any of the common expedients employed in the electrodeposition art may be applied to the electrodeposition of plutonium in accordance with the present invention. The electrodes may be constructed of any conducting material which is inert with respect to its surrounding electrolyte under the operating conditions. Although carbon or other non-metallic electrodes may be used, metallic electrodes, and especially metallic electrodes having amor- 2,830,939 Patented Apr. 15, 1958 phous surfaces, are generally preferred. The electrodes may be of any suitable shape and may be fixed or rotated or otherwise moved in the electrolyte as desired.

The operating potential and electrode-spacing should be correlated in conformity with theconductivity of the particular solution employed to produce as high a current density as is compatible with satisfactory plutonium deposition. With aqueous solutions the current density may range from 1.0 milliampere to 1.0 ampere or more per sq. cm. of cathode surface.

The electrodeposition may be effected over a considerable range of temperature, from ordinary atmospheric temperatures to temperatures substantially below the boiling point of the solution employed. Temperatures of 10-60 C. will generally be satisfactory, but I usually prefer to eifect the electrode-position at a temperature of 20-30 C.

At the conclusion of the electrodeposition, the electrodes should, of course, be removed promptly from the electrolyte to prevent redissolution of the'deposit or attack of the electrodes by the electrolyte. The plutonium deposit may then be removed from its electrode by any suitable means, such as by scraping or other mechanical means, or by the use of an acid or other solvent to form a solution for further processing.

The following example illustrates the separation of plutonium from an aqueous solution by electrodeposition:

Example Serial Number 637,487, filed December 27, 1945.

What is claimed is:

The process of separating plutonium values from an aqueous solution by electrodeposition, which comprises subjecting an aqueous 0.1-1.0 N nitric acid solution containing plutonium ions to electrolysis between metallic electrodes which are inert to said solution under the electrolyzing conditions, with a current density of one milliampere to one ampere per square centimeter of cathode surface, at a temperature of between 10 and 60 C. whereby said plutonium values are electrodeposited on the cathode surface, and recovering said plutonium values.

References Cited in the file of this patent UNITED STATES PATENTS 2,358,029 Phillipsetal Sept. 12, 1944 2,391,353 Sheridan Dec. 18, 1945 OTHER REFERENCES Pierle: The Electrochemistry of Uranium and the Single Potentials of Some Oxides, J. Phy. Chem., 23,

Chamberlain et al.: Range Measurements of 94-239 and 94 -238, U. S. A. E. C. MDDC-489, LADC-258,

Manuscript dated June 26, 1943; declassified Nov. 4, 1946; 2 pages.

Chem. Eng. News, vol. 23, p. 2192 (1945). Hufford et al.: MDDC-1515 Techniques for the Preparation of Thin Films of Radioactive Material, U. S. A. E. 6., Manuscript date November 2, 1945, declassified December 12, 1947; 57 pages. 

